1. Field of the Invention
The present invention relates to three dimensional (hereinafter referred to as “3D”) image processing technology for combining a first and second patches (or objects), which are comprised of a plurality of polygons respectively, to be applied to a video game machine, for example.
2. Description of the Related Art
Various game machines which display a plurality of objects, such as characters, in a pseudo 3D space created on a monitor screen are currently popular. To display game images in such a game machine, the vertex coordinates of polygons constituting an object (or a patch, which is a part of an object) are stored in a storage means, such as a CD-ROM, of the game machine in advance, the vertex coordinates of the object (or patch) in the field of view from the virtual camera viewpoint are read from the storage means, patched in the virtual 3D space, then is perspective-transformed into two-dimensional images, and is displayed on the monitor.
In order to realistically display complicated shaped objects, on the other hand, the number of polygons constituting a polygon model to express an object must be increased. Whereas for a simple shaped object (or patch), it is not desirable to increase the number of polygons, since this increases memory requirements and load of the CPU. So conventionally, the number of polygons constituting an object (or patch) is determined according to the shape of the object (or patch).
However, when objects (or patches) having a different number of polygons (number of vertexes of polygons) are patched in a virtual 3D space, a clearance, as shown in FIG. 12, is generated. FIG. 12 is an example of a diagram describing a clearance generated when two patches having a different number of polygons (number of vertexes of polygons) are patched. In FIG. 12, when the patch PM1 at the left and the patch PM2 at the right are combined, the clearance CL1 is generated at a position combining the patch PM1 and the patch PM2, since the patch PM1 has 10 vertexes, PV 101–PV 110, which become the target of combining, and the patch PM2 has 8 vertexes, PV 201–PV 208, which become the target of combining, (that is, the number of vertexes of polygons to be the combining target is different).
In this way the clearance, which is generated when objects (or patches) are combined, deteriorates the image quality of the game image, spoiling the reality of the image.